Therapeutic nucleosides

ABSTRACT

The present invention relates to 6-substituted purine carbocyclic nucleosides and their use in medical therapy particularly in the treatment of HIV and HBV infections. Also provided are pharmaceutical formulations and processes for the preparation of compounds according to the invention.

This is a continuation-in-part of U.S. application Ser. No. 07/371,870,filed June 26, 1989 now abandoned.

The present invention relates to purine nucleoside analogs containing anunsaturated carbocyclic ring in place of the sugar residue,pharmaceutically acceptable derivatives thereof, and their use inmedical therapy, particularly for the treatment of certain viralinfections.

AIDS (acquired immunodeficiency syndrome) is an immunosuppressive orimmunodestructive disease that predisposes subjects to fatalopportunistic infections. Characteristically, AIDS is associated with aprogressive depletion of T-cells, especially the helper-inducer subsetbearing the OKT⁴ surface marker.

Human immunodeficiency virus (HIV) has been reproducibly isolated frompatients with AIDS or with the symptoms that frequently precede AIDS.HIV is cytopathic and appears to preferentially infect and destroyT-cells bearing the OKT⁴ marker, and it is now generally recognized thatHIV is the etiological agent of AIDS.

Since the discovery that HIV is the etiological agent of AIDS, numerousproposals have been made for anti-HIV chemotherapeutic agents that maybe effective in treating AIDS sufferers. Thus, for example, U.S. Pat.No. 4,724,232 describes 3'-azido-3'-deoxythymidine (which has theapproved name zidovudine), its pharmaceutically acceptable derivativesand their use in the treatment of human retrovirus infections includingAIDS and associated clinical conditions. Vince et al., AntiviralResearch, 9 (1/2), 120 (1988) describes certain carbocyclic nucleosideanalogs and their use against HIV. At the Second InternationalConference on Antiviral Research, Williamsburg, Va., Apr. 10-14, 1988,(±)-9-(cis-4-(hydroxymethyl)-2-cyclopentenyl)guanine (NSC-614846), alsoknown as carbovir, was disclosed.

Worldwide, hepatitis B virus (HBV) is a viral pathogen of majorconsequence. It is most common in Asian countries, and prevalent insub-Saharan Africa. The virus is etiologically associated with primaryhepatocellular carcinoma and is thought to cause 80% of the world'sliver cancer. In the United States more than ten thousand people arehospitalized for HBV illness each year, an average of 250 die withfulminant disease.

The United States currently contains an estimated pool of 500,000-1million infectious carriers. Chronic active hepatitis will develop inover 25% of carriers, and often progresses to cirrhosis. It is estimatedthat 5000 people die from HBV-related cirrhosis each year in the U.S.A.,and that perhaps 1000 die from HBV-related liver cancer. Even when auniversal HBV vaccine is in place, the need for effective anti-HBVcompounds will continue. The large reservoir of persistently infectedcarriers, estimated at 220 million worldwide, will receive no benefitfrom vaccination and will continue at high risk for HBV-induced liverdisease. This carrier population serves as the source of infection ofsusceptible individuals perpetuating the instance of diseaseparticularly in endemic areas or high risk groups such as IV drugabusers and homosexuals. Thus, there is a great need for effectiveantiviral agents, both to control the chronic infection and reduceprogression to hepatocellular carcinoma.

Clinical effects of infection with the HBV virus range from headache,fever, malaise, nausea, vomiting, anorexia and abdominal pains.Replication of the virus is usually controlled by the immune response,with a course of recovery lasting weeks or months in humans, butinfection may be more severe leading to persistent chronic liver diseaseas outlined above. In "Viral Infections of Humans" (second edition, Ed.,Evans, A. S. (1982) Plenum Publishing Corporation, New York), Chapter 12describes in detail the etiology of viral hepatitis infections.

Hepatitis B virus (HBV) is a small DNA containing virus which infectshumans. It is a member of the class of closely related viruses known asthe hepadnaviruses, each member of which selectively infects eithermammalian or avian hosts, such as the woodchuck and the duck. Recentinsights into the mechanism of replication of the hepadnavirus genomeindicate the importance of reverse transcription of an RNA intermediate,suggesting that the reverse transcriptase is a logical chemotherapeutictarget.

It has now been discovered that certain purine nucleoside analoguescontaining an unsaturated carbocyclic ring, as referred to below, areuseful for the treatment of viral infections, for example, hepatitis Band retroviral infections, especially AIDS.

According to a feature of the present invention, novel compounds of theformula (I) are provided: ##STR1## wherein R³ represents hydrogen orC₁₋₆ alkyl; R⁶ represents C₃₋₈ cycloalkyl (preferably C₃₋₆ cycloalkyl,e.g. cyclopropyl, cyclobutyl or cyclopentyl); and R⁷ represents ahydrogen atom or branched or straight chain C₁₋₆ alkyl (e.g. methyl orethyl); or a pharmaceutically acceptable derivative thereof.

The most preferred isomers are those in which the hydroxymethyl group iscis to the purine in compounds of formula (I). It is to be understoodthat the present invention encompasses the individual enantiomers of thecompounds of formula (I) as well as wholly or partially racemic mixturesof such enantiomers even though the precise structures as drawn relateto one enantiomer.

Preferred examples of compounds of formula (I) are:

a)(-)-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanoland racemic or partially resolved mixtures with the (+)-cis enantiomerthereof and

b)(-)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanoland racemic or partially resolved mixtures with the (+)-cis enantiomerthereof.

These compounds are particularly preferred because of the high levelswhich reach the central nervous system where manifestations of HIVinfection are particularly debilitating.

The compounds of formula (I) above and their pharmaceutically acceptablederivatives are hereinafter referred to as the compounds according tothe invention.

In one aspect of the invention there are provided the compoundsaccording to the invention for use in medical therapy particularly forthe treatment of retroviral infections and heptatis B viral infections.

Examples of retroviral infections which may be treated or prevented inaccordance with the invention include human retroviral infections suchas human immunodeficiency virus (HIV), HIV-1, HIV-2 and human T-celllymphotropic virus (HLTV), e.g. HTLV-I or HTLV-II infections. Thecompounds according to the invention are especially useful for thetreatment of AIDS and related clincial conditions such as AIDS-relatedcomplex (ARC), progressive generalised lymphadenopathy (PGL),AIDS-related neurological conditions, such as multiple sclerosis ortropical paraparesis, anti-HIV antibody-positive and HIV-positiveconditions and thrombocytopenic purpura. The compounds may also be usedin the treatment or prevention of psoriasis.

The compounds of the present invention are particularly applicable forthe treatment of asymptomatic infections or diseases in humans caused byor associated with human retroviruses.

In a further aspect of the present invention there is included:

a) A method for the treatment of retroviral infections and hepatitis Binfections which comprises treating the subject with a therapeuticallyeffective amount of a compound according to the invention.

b) Use of a compound according to the invention in the manufacture of amedicament for the treatment of any of the above-mentioned infections orconditions.

By "a pharmaceutically acceptable derivative" is meant anypharmaceutically or pharmacologically acceptable salt, ester or salt ofsuch ester, of a compound according to the invention or any othercompound which, upon administration to the recipient, is capable ofproviding (directly or indirectly) a compound according to theinvention, or an antivirally active metabolite or residue thereof.

Preferred esters of the compounds of the invention include carboxylicacid esters in which the non-carbonyl moiety of the ester grouping isselected from straight or branched chain alkyl, e.g. n-propyl, t-butyl,n-butyl, alkoxyalkyl (e.g. methoxymethyl), aralkyl (e.g. benzyl),aryloxyalkyl (e.g. phenoxymethyl), aryl (e.g. phenyl optionallysubstituted by halogen, C₁₋₄ alkyl or C₁₋₄ alkoxy or amino); sulfonateesters such as alkyl- or aralkylsulfonyl (e.g. methanesulfonyl); aminoacid esters (e.g. L-valyl or L-isoleucyl); and mono-, di- ortriphosphate esters. The phosphate esters may be further esterified by,for example, a C₁₋₂₀ alcohol or reactive derivative thereof, or by a2,3-di(C₆₋₂₄)acyl glycerol.

With regard to the above-described esters, unless otherwise specified,any alkyl moiety present advantageously contains 1 to 18 carbon atoms,particularly 1 to 4 carbon atoms. Any aryl moiety present in such estersadvantageously comprises a phenyl group.

Any reference to any of the above compounds also includes a reference toa pharmaceutically acceptable salt thereof.

Examples of pharmaceutically acceptable salts of the compounds accordingto the invention and pharmaceutically acceptable derivatives thereofinclude base salts, e.g. derived from an appropriate base, such asalkali metal (e.g. sodium), alkaline earth metal (e.g. magnesium) salts,ammonium and NW+₄ (wherein W is C₁₋₄ alkyl). Physiologically acceptablesalts of a hydrogen atom or an amino group include salts of organiccarboxylic acids such as acetic, lactic, tartaric, malic, isethionic,lactobionic and succinic acids; organic sulfonic acids such asmethanesulfonic, ethanesulfonic, benzenesulfonic and p-toluenesulfonicacids and inorganic acids such as hydrochloric, sulfuric, phosphoric andsulfamic acids. Physiologically acceptable salts of a compound with ahydroxy group include the anion of said compound in combination with asuitable cation such as Na+, NH₄ +, and NW₄ + (wherein W is a C₁₋₄ alkylgroup).

The above compounds according to the invention and theirpharmaceutically acceptable derivatives may be employed in combinationwith other therapeutic agents for the treatment of the above infectionsor conditions. Examples of such further therapeutic agents includeagents that are effective for the treatment of viral infections orassociated conditions such as 3'-azido-3'-deoxythymidine (zidovudine),2',3'-dideoxynucleosides such as 2',3'-dideoxycytidine,2',3'-dideoxydenosine and 2',3'-dideoxyinosine, acyclic nucleosides(e.g. acyclovir), interferons such as α-interferon, renal excretioninhibitors such as probenicid, nucleoside transport inhibitors such asdipyridamole, dilazep, mio-, lido- or soluflazine, or hexobendine aswell as immunomodulators such as interleukin II and granulocytemacrophage colony stimulating factors, soluble CD₄ or geneticallyengineered derivatives thereof, and phosphonoformic acid. The componentcompounds of such combination therapy may be administeredsimultaneously, in either separate or combined formulations, or atdifferent times, e.g. sequentially such that a combined effect isachieved.

The compounds according to the invention, also referred to herein as theactive ingredient, may be administered for therapy by any suitable routeincluding oral, rectal, nasal, topical (including buccal andsublingual), vaginal and parenteral (including subcutaneous,intramuscular, intravenous and intradermal). It will be appreciated thatthe preferred route will vary with the condition and age of therecipient, the nature of the infection and the chosen active ingredient.

In general a suitable dose for each of the above-mentioned conditions(e.g. AIDS) will be in the range of 3.0 to 120 mg per kilogram bodyweight of the recipient (e.g. a human) per day, preferably in the rangeof 6 to 90 mg per kilogram body weight per day and most preferably inthe range 15 to 60 mg per kilogram body weight per day. The desired doseis preferably presented as two, three, four, five, six or more sub-dosesadministered at appropriate intervals throughout the day. Thesesub-doses may be administered in unit dosage forms, for example,containing 10 to 1500 mg, preferably 20 to 1000 mg, and most preferably50 to 700 mg of active ingredient per unit dosage form.

Ideally, the active ingredient should be administered to achieve peakplasma concentrations of the active compound of from about 1 to about 75μM, preferably about 2 to 50 μM, most preferably about 3 to 30 μM. Thismay be achieved, for example, by the intravenous injection of a 0.1 to5% solution of the active ingredient, optionally in saline, or orallyadministered as a bolus containing about 1 to about 100 mg/kg of theactive ingredient. Desirable blood levels may be maintained by acontinuous infusion to provide about 0.01 to about 5.0 mg/kg/hour or byintermittent infusions containing about 0.4 to about 15 mg/kg of theactive ingredient.

While it is possible for the active ingredient to be administered aloneit is preferable to present it as a pharmaceutical formulation. Theformulations of the present invention comprise at least one activeingredient, as defined above, together with one or more acceptablecarriers thereof and optionally other therapeutic agents. Each carriermust be "acceptable" in the sense of being compatible with the otheringredients of the formulation and not injurious to the patient.Formulations include those suitable for oral, rectal, nasal, topical(including buccal and sublingual), vaginal or parenteral (includingsubcutaneous, intramuscular, intravenous and intradermal)administration. The formulations may conveniently be presented in unitdosage form and may be prepared by any methods well known in the art ofpharmacy. Such methods include the step of bringing into association theactive ingredient with the carrier which constitutes one or moreaccessory ingredients. In general, the formulations are prepared byuniformly and intimately bringing into association the active ingredientwith liquid carriers or finely divided solid carriers or both, and thenif necessary shaping the product.

Formulations of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, cachets or tabletseach containing a predetermined amount of the active ingredient; as apowder or granules; as a solution or a suspension in an aqueous ornon-aqueous liquid; or as an oil-in-water liquid emulsion or awater-in-oil liquid emulsion. The active ingredient may also bepresented as a bolus, electuary or paste.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared bycompressing in a suitable machine the active ingredient in afree-flowing form such as a powder or granules, optionally mixed with abinder (e.g. povidone, gelatin, hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (e.g. sodium starchglycollate, cross-linked povidone, cross-linked sodium carboxymethylcellulose) surface-active or dispersing agent.

Molded tablets may be made by molding in a suitable machine a mixture ofthe powdered compound moistened with an inert liquid diluent. Thetablets may optionally be coated or scored and may be formulated so asto provide slow or controlled release of the active ingredient thereinusing, for example, hydroxypropylmethyl cellulose in varying proportionsto provide the desired release profile. Tablets may optionally beprovided with an enteric coating, to provide release in parts of the gutother than the stomach. This is particularly advantageous for purinenucleoside derivatives as such compounds are susceptible to acidhydrolysis.

Formulations suitable for topical administration in the mouth includelozenges comprising the active ingredient in a flavored basis, usuallysucrose and acacia or tragacanth; pastilles comprising the activeingredient in an inert basis such as gelatin and glycerin, or sucroseand acacia; and mouthwashes comprising the active ingredient in asuitable liquid carrier.

Formulations for rectal administration may be presented as a suppositorywith a suitable base comprising for example cocoa butter or asalicylate.

Formulations suitable for vaginal administration may be presented aspessaries, tampons, creams, gels, pastes, foams or spray formulationscontaining in addition to the active ingredient such carriers as areknown in the art to be appropriate.

Formulations suitable for parenteral administration include aqueous andnon-aqueous isotonic sterile injection solutions which may containanti-oxidants, buffers, bacteriostats and solutes which render theformulation isotonic with the blood of the intended recipient; andaqueous and non-aqueous sterile suspensions which may include suspendingagents and thickening agents. The formulations may be presented inunit-dose or multidose sealed containers, for example, ampules andvials, and may be stored in a freeze-dried (lyophilized) conditionrequiring only the addition of the sterile liquid carrier, for examplewater for injections, immediately prior to use. Extemporaneous injectionsolutions and suspensions may be prepared from sterile powders, granulesand tablets of the kind previously described.

Preferred unit dosage formulations are those containing a daily dose orunit, daily sub-dose, as herein above recited, or an appropriatefraction thereof, of an active ingredient.

The compounds according to the invention may also be presented for usein the form of veterinary formulations, which may be prepared, forexample, by methods that are conventional in the art.

It should be understood that in addition to the ingredients particularlymentioned above the formulations of this invention may include otheragents conventional in the art having regard to the type of formulationin question, for example, those suitable for oral administration mayinclude such further agents as sweeteners, thickeners and flavoringagents.

The present invention further includes a process for the preparation ofa compound according to the invention and pharmaceutically acceptablederivatives thereof which comprises either:

A) treating a compound of formula (II) ##STR2## wherein R³ is ashereinbefore defined and Z represents a precursor group for the NR⁶ R⁷group as defined in formula (I) with an agent or under conditionsserving to convert the precursor Z group to the desired R² group; or

B) reacting a compound of formula ##STR3## wherein R⁶ and R⁷ arehereinbefore defined, R⁸ is hydrogen or formyl, and R⁹ is a C₁₋₆ acylgroup (e.g., formyl or acetyl) or a pharmaceutically acceptablederivative thereof, with an agent serving to effect formation of theimidazole ring in the desired compound of formula (I); or

i) where a compound of formula (I) is formed, converting the saidcompound to a pharmaceutically acceptable derivative thereof; or

ii) where a pharmaceutically acceptable derivative of a compound offormula (I) is formed, converting the said derivative to the parentcompound of formula (I) or to a further such derivative.

Process A) above may be carried out in conventional manner, for example,by treatment of a compound of formula (II) in which Z represents aleaving group (e.g. a halo such as a chloro group) with an appropriateamine or amine hydrochloride to introduce a substituted amino group asdefined above at reflux or at a temperature greater than 50° C.,preferably in the presence of an organic solvent, for example methanolor ethanol.

Process B) may be carried out, for example, by reacting a compound offormula (III) with formic acid or a reactive formic acid derivative(e.g. triethylorthoformate or diethoxymethyl acetate) in a solvent suchas a dimethylacetamide or dimethylformamide at an elevated temperature,preferably at 75°-90° C. This reaction is conveniently effected by theaddition of slightly more than one equivalent of a strong anhydrousacid, e.g. with 1.1 equivalents of ethanesulfonic acid per equivalent ofcompound of formula (III), in which case lower temperatures (e.g. 25°C.) are used.

In process A) the starting material of formula (II) may be prepared, forexample, by firstly cyclizing a compound of formula (III) above in ananalogous manner to that described for process B) above.

Other reagents may be useful for cyclization of compounds of formula(III) to give compounds of formula I where R₃ is not hydrogen. Forexample, triethyl or trimethylorthoacetate with acetic anhydride at70°-120° C. for several hours gives R₃ ═CH₃ (see H. C. Koppel and R. K.Robins, J. Org. Chem. 1958, 1457).

Alternatively, (1R,4S)-9-(4-hydroxymethyl-2-cyclopentenyl)guanine,prepared, e.g. as described in Australian patent applicationAU-A-28671/89 (incorporated hereinby reference) from aristeromycin, maybe converted to compounds of formula (I).

A compound of formula (I) may be converted into a pharmaceuticallyacceptable ester by reaction with an appropriate esterifying agent, e.g.an acid halide or anhydride. The compound of formula (I), includingesters thereof, may be converted into pharmaceutically acceptable saltsthereof in conventional manner, for example, by treatment with anappropriate acid. An ester or salt of a compound of formula (I) may beconverted into the parent compound, for example by hydrolysis.

The enantiomers of the compounds of formula (I) may be resolved orisolated in conventional manner, e.g. by chromatographic separation ofdiastereomeric esters prepared by acylation of the hydroxyl on thecyclopentenyl moiety with appropriate optically active carboxylic acidderivatives as, e.g., with naproxen (J. Org. Chem. 1986, 51, 1287). Thecyclopentenyl precursors of the compounds of formula (III), may also beresolved by fractional crystallization of salts formed with opticallyactive carboxylic acids (e.g. dibenzoyl-D-tartaric acid). Alternatively,enzymatic resolution may be achieved as in J. Med. Chem. 1987, 30, 746and J. Med. Chem. 1985, 28, 1385.

The following Examples are intended for illustration only and are notintended to limit the scope of the invention in any way. The term`active ingredient` as used in the Examples means a compound of formula(I) or a pharmaceutically acceptable derivative thereof.

EXAMPLE 1(±)-cis-4-[(2-Amino-4-chloro-6-pyrimidinyl)amino]-2-cyclopentene-1-methanol

cis-4-Acetamidocyclopent-2-enemethyl acetate [U.S. Pat. No. 4,268,672](14.88 g, 0.073 mol) and barium hydroxide octahydrate (46.19 g, 0.146mol) were refluxed in water (300 mL) under nitrogen for 18 hours. Theresulting solution was neutralized with carbon dioxide. The precipitatewas washed with water, then ethanol. The combined filtrate-wash wasevaporated to a syrup (11.16 g) which was condensed with2-amino-4,6-dichloropyrimidine (23.91 g, 0.146 mol) and triethylamine(30.5 mL, 0.219 mol) in refluxing 1-butanol (100 mL) for 1.5 hours.After addition of 1N NaOH (73 mL), the resulting mixture was evaporatedto dryness and the residual solid slurried in CHCl₃ (200 mL). Unreacted2-amino-4,6-dichloropyrimidine was filtered off and washed withchloroform (100 mL). The chloroform filtrate-wash was concentrated andchromatographed on a silica gel column. Additional pyrimidine startingmaterial was eluted with 2.5% methanol-chloroform. The title compoundwas eluted with 3.5% methanol-chloroform as an off-white solid foam(15.90 g, 91%).

¹ H-NMR: (Me₂ SO-d₆) δ1.15-1.28 and 2.26-2.41 (2m, 2, CH₂); 2.60-2.71(m, 1, 1'-H); 3.4 (m overlapping H₂ O, CH₂ OH); 4.625 (t, J=5.3, 1, CH₂OH); 4.95 (br s, 1, CH--N); 5.67-5.87 (m, 2, CH═CH); 6.38 (br s, 1,NH₂); 7.12 (br s, 1, NH); MS (CI) M+1, 241, 243.

Anal. Calcd. for C₁₀ H₁₃ N₄ OCl.0.2H₂ O: C, 48.99; H, 5.55; N, 22.85;Cl, 14.46. Found: C, 49.10; H, 5.57; N, 22.81; Cl, 14.40.

EXAMPLE 2(±)-cis-4-[[2-Amino-6-chloro-5-[(4-chlorophenyl)azo]-4-pyrimidinyl]amino]-2-cyclopentene-1-methanol

(±)-cis-4-[(2-Amino-4-chloro-6-pyrimidinyl)amino]-2-cyclopentene-1-methanolfrom Example 1 (11.58 g, 48.1 mmol) and sodium acetate trihydrate (97 g)were dissolved in glacial acetic acid (225 mL) and water (225 mL). Acold solution (0°-5° C.) of 4-chlorobenzenediazonium chloride wasprepared from 4-chloroaniline (6.74 g, 52.8 mol), concentratedhydrochloric acid (14.7 mL) water (52 mL), and sodium nitrite (4.01 g,58.2 mmol in 47 mL of water). This cold solution was added dropwise over5 minutes to the first solution. The resulting yellow precipitate wasfiltered after 18 hours, washed with water, and extracted with ethanolto give title compound as dark yellow powder (12.56 g, 69%), m.p.218°-220° C. dec.

¹ H-NMR: (Me₂ SO-d₆) δ10.25 (d, 1, NH); 7.69 and 7.54 (both, d, J=8.9,C₆ H₄) overlapping 7.6 (br, 6, NH₂); 5.80-5.95 (m, 2, CH═CH); 5.24 (m,1, CHN); 4.75 (t, 1, CH₂ OH); 3.41 (t, 2, CH₂ OH); 2.75 (m, 1, CH); 2.41(m, 1, CH); 1.44-1.53 (m, 1, CH).

Anal. Calcd. for C₁₆ H₁₆ N₆ Cl₂ O: C, 50.67; H, 4.25; N, 22.16; Cl,18.70. Found: C, 50.59; H, 4.29; N, 22.10; Cl, 18.66.

EXAMPLE 3(±)-cis-4-[(2,5-Diamino-4-chloro-6-pyrimidinyl)-amino]-2-cyclopentene-1-methanol

The title compound of Example 2 (11.67 g) was suspended in ethanol (235mL), glacial acetic acid (30 mL), and water 235 mL). The mixture washeated to reflux under nitrogen. Zinc dust (13.5 g) was added in smallportions over 30 minutes during which time the compound dissolved. Thereaction was heated an additional 20 minutes, and then the excess zincwas filtered of from the hot solution, and it was washed with ethanol.The filtrates were evaporated, and the residue was purified on a silicagel column eluting with chloroform (1 L) and chloroform:methanol/4:1(1.8 L). The fractions containing the product were combined, and thesolvent was removed under reduced pressure to give the title compound asa red-orange oil (11.2 g, >100% yield). A pure sample was obtainedduring another small scale reaction to obtain the product as a lightyellow solid in a 76% yield.

¹ H-NMR: (Me₂ SO-d₆) δ1.29 and 2.39 (m, 2, CH₂); 2.69 (t, 1, 1'-H); 3.37(d, 2, CH₂ OH); 3.91 (br, 2, NH₂); 4.60 (br, 1, CH₂ OH); 5.02 (m, 1,CHNH); 5.56 (br s, 2, NH₂); 5.74 (m, 1, ═CH); 5.86 (m, 1, ═CH); 6.36 (d,1, CHNH).

EXAMPLE 4(±)-cis-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol

The title compound of Example 3 (about 9.7 g) was dissolved indiethoxymethyl acetate (100 g), and refluxed for two days. The solventwas removed under high vacuum at 50° C., and dioxane (40 mL) and 0.5NHCl (60 mL) was added. The reaction was stirred at room temperature for1.25 hours, and then chilled. The reaction was neutralized to pH 7 withcold 5N sodium hydroxide, and then it was extracted withchloroform:methanol/3:1 several times. The organic layers were driedwith magnesium sulphate, filtered, and evaporated. The residue waspurified by chromatography on a silica gel column, eluting with 2%MeOH-CHCl₃ to give 3.7 g (46% yield) of the title compound, m.p.138°-139° C.

¹ H-NMR: (Me₂ SO-d₆) δ1.63 and 2.61 (m, 2, CH₂); 2.87 (m, 1, 1'-H); 3.44(d, 2, CH₂ OH); 5.44 (m, 1, CH--N); 5.89 (m, 1, ═CH); 6.14 (m, 1, ═CH);6.82 (br s, 2, NH₂); 8.02 (s, 1, 8-H); (CH₂ OH not seen--under H₂ Opeak). UV: pH 1 λ_(max) 315 (ε7370); 218 (26200); λsh 239.5 (5650). pH7.4 λ_(max) 307 (ε8000); 245.5 (4600); 223 (26400). MS (EI) 265, 267 (m)(CI) 266, 268 (m+1).

Anal. Calcd. for C₁₁ H₁₂ N₅ Cl0.2H₂ O: C, 43.79; H, 5.35; N, 23.21; Cl,11.75. Found: C, 43.67; H, 5.29; N, 23.05; Cl, 11.70.

EXAMPLE 5(±)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 4 (0.50 g) was dissolved in ethanol (40mL), and cyclopropylamine (0.65 mL, 5 equivalent) was added. Thereaction was refluxed under nitrogen for 6 hours. An additional 0.65 mLof cyclopropylamine was added, and the reaction refluxed for anadditional 5.5 hours. The solvents were evaporated, and chloroform (25mL) and saturated sodium bicarbonate solution (5 mL) was added. Theaqueous layer was extracted several times with CHCl₃ to obtain the crudeproduct. This was purified on a silica gel column eluting with 3%methanol-ethyl acetate to give 0.43 g (80%) of(±-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol.This was recrystallized from acetonitrile to give 0.30 g of whitepowder; m.p. collapses at 93°-130° C.; melts at 165° C.

¹ H-NMR: (Me₂ SO-d₆) δ0.56 and 0.63 (2m, 4, 2-cyclopropyl CH₂); 1.56 and2.60 (2m, 2, cyclopentenyl-CH₂); 2.85 (m, 1, 1'-H); 3.02 (m, 1,cyclopropyl CH--NH); 3.43 (m, 2, CH₂ OH); 4.71 (t, 1, CH₂ OH); 5.40 (m,1, 4'-H); 5.77 (s, 2, NH₂), overlapping 5.84 (m, 1, ═CH₂); 6.09 (m, 1,═CH); 7.23 (d, 1, NH--CH); 7.58 (s, 1, purine-8-H); ms (CI) 287 (m+1).UV: pH 1: λ_(max) 296 (ε14000), 255 (10700); pH 7.0: λ_(max) 284(15900); 259 (9200); pH 13: λ_(max) 284 (15800), 259 (9100).

Anal. Calcd. for C₁₄ H₁₈ N₆ O.0.25H₂ O: C, 57.82; H, 6.41; N, 28.90.Found: C, 57.84; H, 6.45; N, 28.86.

EXAMPLE 6(±)-cis-4-(2-Amino-6-cyclopentylamino-9H-purin-9-yl)-2-cyclopentene-1-methanol

A solution of(±)-cis-4-(-2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol(0.53 g, 2 mmol) from Example 4, triethylamine (2.00 g, 20 mmol),cyclopentylamine (267 mg, 3.1 mmol) and ethanol (10 mL) was stirred atreflux for 9 hours. The solution was allowed to cool to room temperaturebefore the addition of 2 mL of 1.0N NaOH. Concentration of the solutionafforded the crude product which was purified by elution from a silicagel column using 5% methanol in chloroform (0.430 g, 68.4%).Crystallization of such a sample from ethanol-acetonitrile gave anoff-white powder, m.p. 143°-146° C.

¹ H-NMR: (Me₂ SO-d₆) δ7.60 (s, 1H, purine H-8), 7.00 (br, m, 1H, NH)6.10 and 5.86 (m, 2H, CH═CH), 5.77 (br s, 2H, NH₂) 5.39 (m, 1H, NCHcyclopentene), 4.76 (br s, 1H, OH), 4.53 (br m, 1H, NCH), 3.44 (m, 2H,OCH₂), 2.87 (m, 1H, CH) 2.62-2.54 (m, 1H, 0.5CH₂ cyclopentene ring),1.89 (br m, 2H, cyclopentyl CH₂), 1.70-1.48 (br, m, 7H, 0.5CH₂cyclopentene ring, 3CH₂).

Anal. Calcd. for C₁₆ H₂₂ N₆ O.0.25H₂ O: C, 60.26; H, 7.11; N, 26.35.Found: C, 60.43, 60.37; H, 7.16, 7.17; N, 26.27, 26.25.

EXAMPLE 7(±)-cis-4-(2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanol

(±)-cis-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol(0.53 g, 2 mmol) from Example 4, N-methyl-N-cyclopropylamine (KarlIndustries, Aurora, OH; 0.8477 g, 12 mmol) and methanol (20 mL) wereplaced in a Parr bomb and heated to 62° C. for 5 hours. The solution wasconcentrated and then diluted with ethanol before being brought to pH 12by the addition of 1.0N NaOH. This solution was concentrated and theresidue was purified by elution from a silica gel column with 3%methanol-chloroform (0.547 g, 91.2%). Crystallization of such a samplefrom water-ethanol yielded a white powder, m.p. 130°-131° C.

¹ H-NMR: (Me₂ SO-d₆) δ7.61 (s, 1H, purine H-8), 6.10 (m, 1H, CH═), 5.84(m, 1H, CH═), 5.7 (br s, 2H, NH₂), 5.40 (m, 1H, CHN), 4.70 (br t, 1H,OH), 3.43 (m, 2H, CH₂ OH) 3.24 (br s, 4H, CH₃, NCH cyclopropyl), 2.85(m, 1H, CH), 2.66-2.57 and 1.61-1.51 (m, 2, cyclopentenyl CH₂),0.90-0.65 (m, 4H, 2CH₂ of cyclopropyl).

Anal. Calcd. C₁₅ H₂₀ N₆ O.0.5H₂ O: C, 58.24; H, 6.84; N, 27.16. Found:C, 58.15; H, 6.86; N, 27.14.

EXAMPLE 8(±)-cis-4-(2-Amino-6-cyclobutylamino-9H-purin-9-yl)-2-cyclopentene-1-methanol

A solution of(±)-cis-4-(-2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 4 (0.53 g, 2 mmol) and cyclobutylamine (1.387 g, 19.5 mmol)in methanol (15 mL) was heated at 70°-75° C. (oil bath) for 29 hours.After cooling to room temperature, 2 mL of 1.0N NaOH was added. Thesolution was concentrated and the residue chromatographed on silica gel.Title compound was eluted with 5% methanol-chloroform as colourless foamwhich solidified to white powder in acetonitrile (454 mg, 75.7%), m.p.181°-183° C.

¹ H-NMR: (DMSO-d₆) δ7.59 (s, 1H, purine H.8), 7.38 (br m, 1H, NH), 6.10(m, 1H 0.5HC═CH) 5.84 (m overlapping br s, at 5.76, 3H, 0.5CH═CH, NH₂)5.36 (m, 1H, NCH cyclopentene), 4.73 (t, overlapping br m, J=5.2, 2H,OH, NCH cyclobutane), 3.42 (m, 2H, OCH₂), 2.83 (br m, 1H, CH), 2.55 (moverlapping with DMSO, 1/2CH₂ cyclopentene), 2.20-1.95 (br m, 4H, 2CH₂cyclobutane), 1.58 (m, 3, CH₂ cyclobutane, 0.5CH₂ cyclopentene).

Anal. Calcd. C₁₅ H₂₀ N₆ O: C, 59.98; H, 6.71; N, 27.98. Found: C, 60.05;H, 6.73; N, 27.91.

EXAMPLE 9(±)-cis-[4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopenten-1-yl]-methylacetate

A solution of(±)-cis-4-(2-amino-6-cyclopropylamino-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 5 (400 mg, 1.5 mmol), acetic anhydride (228 mg, 2.2 mmol),4-N,N-dimethylaminopyridine (8.4 mg, 6.9 10⁻² mmol) and dryN,N-dimethylformamide (12 mL) were stirred at room temperatureovernight. The solution was concentrated under high vacuum and theresidues were placed on a silica gel column which was eluted with 5%methanol-chloroform, (240 mg, 48.7%). The title compound was diluted inethanol and foamed under high vacuum.

¹ H-NMR: (DMSO-d₆) δ7.52 (s, 1H, purine H8), 7.28 (d, J=4.5, 1H, NH),6.07 and 5.94 (m, 2H, HC═CH) 5.81 (br, 2H, NH₂), 5.39 (br m, 1H, NCH),4.06 (m, 2H, OCH₂) 3.02 (br m, 2H, CH, NCH cyclopropane), 2.65 (m, 1H0.5CH₂ cyclopentene) 1.98 (s, 3H, CH₃), 1.56 (m, 1H, 0.5CH₂cyclopentene), 0.61 (m, 4H, 2CH₂ cyclopropane).

Anal. Calcd. C₁₆ H₂₀ N₆ O₂.0.4H₂ O.0.15EtOH: C, 57.16; H, 6.39; N,24.54. Found: C, 56.88, 56.82; H, 6.32, 6.32; N, 24.81, 24.78.

EXAMPLE 10(±)-cis-[4-(2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-yl]-methylacetate

A solution of (%)-cis-4-(2amino-6-(cyclopropylmethylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 7 (0.30 g, 1 mmol), acetic anhydride (0.204 g, 2 mmol),N,N-dimethylaminopyridine (0.005 g, 0.04 mmol) in N,N-dimethylformamide(10 mL) was stirred at room temperature under nitrogen overnight. H₂ O(1 mL was added and the solution allowed to stir an additional hour,then concentrated under high vacuum. The residual oil was partitionedbetween saturated sodium bicarbonate solution (5 mL) and chloroform(3×50 mL). The combined chloroform extracts were dried (MgSO₄), solventevaporated and residue chromatographed on silica gel. Title compound waseluted with 4% methanol-chloroform; foamed from ethanol under highvacuum (0.330 g, 93%).

¹ H-NMR: (DMSO-d₆) δ7.59 (s, 1, H-8), 6.10 and 5.90 (2m, 2, CH═CH), 5.80(br s, 2, NH₂), 5.40 (br m, 1, CH--N), 4.05 (d, J=6.1, 2, OCH₂),3.30-3.20 (m, overlapping s at 3.23, total 4, CH--N--Me), 3.10 (br m, 1,CH), 2.75-2.60 (m, 1, 0.5CH₂), 1.98 (s, 3, COCH₃), 1.65-1.50 (m, 1,0.5CH₂).

Anal. Calcd. for C₁₇ H₂₂ N₆ O₂.0.45H₂ O0.5EtOH: C, 58.21; H, 6.63; N,23.82. Found: C, 58.15, 58.09; H, 6.60, 6.61; N, 23.91, 23.83.

EXAMPLE 11(±)-cis-4-[2-Amino-6(cyclopropylethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

A sample of N-cyclopropyl-N-ethylamine was prepared as follows.Cyclopropylamine (18.44 g, 0.323 mole), potassium carbonate (45.6 g,0.33 mole), and dry diethyl ether (250 mL) were stirred vigorously withcooling (ice bath) while trifluoroacetic anhydride (50 mL, 0.36 mol) wasadded dropwise over 30 minutes. Ice water (20 mL) was added. The etherlayer was separated and dried (MgSO₄).

Concentration gave a pale yellow liquid (51.1 g). A portion of thisliquid (15.3 g, ca.0.1 mole) was dissolved in dry acetone (250 mL) withethyl iodide (46.8 g, 0.30 mole) and heated to 70° C. (oil bath).Powdered potassium hydroxide (16.8 g, 0.300 equiv.) was added. Stirringwas continued at 70° C. for 30 minutes. Excess ethyl iodide and acetonewere removed by evaporation. Water (100 mL) was added to the residue andthe resulting solution brought to reflux over 15 minutes (oil bath 110°C.) and maintained at reflux for 5 minutes. The solution was cooled to25° C., saturated with sodium chloride, and extracted with diethyl ether(3×100 mL). The ether solution was dried (MgSO₄) and evaporated to leavepale yellow oil (4.86 g, 57%); ¹ H-NMR (DMSO-d₆) δ7.74 (q, J=6.0, 2,NCH₂ CH₃), 2.2-2.08 (m, 1, CHN), 1.97 (br s, NH+H₂ O), 1.19 (t, J=6.0,3, NCH₂ CH₃), 1.9-1.3 (m, 4, 2CH₂). Such a sample ofN-cyclopropyl-N-ethylamine (1.26 g) was heated with(±)-(cis)-4-(2-amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 4 (544 mg, 2.00 mmol) in methanol (16 mL) in a Parr bomb at75° C. for 11.5 hours. Sodium hydroxide (1N, 1.5 mL) was added and thesolution evaporated to dryness. The residue was chromatographed onsilica gel. Title compound was eluted with 4% methanol-chloroform aspale yellow-glass which crystallized from acetonitrile; 298 mg (47%);m.p. 152°-154° C.

¹ H-NMR: (DMSO-d₆) δ7.64 (s, 1H, purine H-8), 6.11 and 5.88 (m, 2,HC═CH), 5.80 (br s, 2, NH₂), 5.42 (m, 1, NCH cyclopentene) 4.75 (t,J=4.8, 1, OH), 3.94 (m, 2, NCH₂), 3.45 (m, 2, OCH₂), 3.05 (m, 1, NCHcyclopropane), 2.87 (br m, 1, CH), 2.60 (m, overlapping with DMSO,0.5CH₂ cyclopentene), 1.56 (m, 1, 0.5CH₂ cyclopentene), 1.10 (t, J=6.9,CH₃), 0.85 and 0.65 (m, 4, 2CH₂).

Anal. Calcd. for C₁₆ H₂₂ N₆ O: C, 61.13; H, 7.05; N, 26.73. Found: C,61.06; H, 7.07; N, 26.66.

EXAMPLE 12(±)-cis-[4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopenten-1-yl]-methylL-valinate trifluoroacetate

N-Butyloxycarbonyl-L-valine (1.200 g, 5.19 mmol) andN,N-dicyclohexyl-carbodiimide (0.562 g, 2.73 mmol) were stirred in drymethylene chloride (46 mL) for 40 minutes. The mixture was filtered, theprecipitate washed with methylene chloride (8 mL), and the filtrate-washevaporated to dryness. This residual white solid (anhydride) was addedin two portions to(±)-cis-4-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 5 (572 mg, 2.00 mmol), dry N,N-dimethylformamide (19 mL)and 4-N,N-dimethylaminopyridine (20 mg, 0.16 mmol). The reaction wasstirred at 25° C. under nitrogen for 69 hours, before the addition ofwater (0.3 mL). The solution was evaporated to dryness and the residuepartitioned between chloroform and NaHCO₃ (2.5 mmol) in H₂ O. Theaqueous layer was extracted with chloroform and the combined organiclayers were dried (MgSO₄), filtered. Elution with 4% methanol-chloroformgave the N-butyloxy-carbonyl-blocked derivative of the title compound aswhite foam (520 mg).

¹ H-NMR: (Me₂ SO-d₆) δ7.62 (s, 1, purine H-8), 7.30 (d, J=3.9, 1, NHcyclopropylamine), 7.16 (d, J=7.9, 1, CHN), 6.08 and 5.95 (m, 2, HC═CH),5.83 (br s, 2, NH₂), 5.42 (br m, 1, NCH), 4.13 (d, J=6.3, 2, OCH₂), 3.82(t, J=7.4, 1, NCH of valyl), 3.08 (br m, 2, CH cyclopentene, CHcyclopropane) 2.69 (m, 1, 0.5CH₂ cyclopentene), 1.97 (m, 1, CHMe₂), 1.60(m, 1, 0.5CH₂ cyclopentene), 1.37 (s, 9, C(CH)₃), 0.88-0.79 (overlappingd, 6, CH(CH₃)₂), 0.64 and 0.59 (m, 4, 2CH₂ cyclopropane). Thisderivative (510 mg) was dissolved in trifluoracetic acid:methylenechloride/1:3 (˜ 25 mL) and the solution stirred at 25° C. for 30minutes. Evaporation left the title compound as a yellow foam (745 mg).

¹ H-NMR: (DMSO-d₆) δ9.85 (br m, 1, NH), 8.37 (br m, 3, NH₃ +), 8.01 (brs, 1, purine H-8), 7.57 (br s, 2, NH₂), 6.17 and 6.02 (m, 2, HC═CH),5.48 (m, 1, NCH cyclopentene), 4.26 (m, overlapping br solvent, OCH₂),3.94 (br m, overlapping solvent, valyl CH), 3.17 (m, 1, CH), 2.9-2.68(br m, 2, cyclopropyl CHN, 0.5CH₂ cyclopentene), 2.14 (m, 1, CHMe₂),1.66 (m, 1, 0.5CH₂ cyclopentene), 0.94 (m, 8, CHMe₂, CH₂ cyclopropane),0.78 (m, 2, cyclopropyl CH₂).

Anal. Calcd. for C₁₉ H₂₇ N₇ O₂.0.8H₂ O.3.8CF₃ CO₂ H: C, 38.35; H, 3.92;N, 11.77. Found: C, 38.25; H, 3.79; N, 11.80.

EXAMPLE 13(±)-cis-4-[2-Amino-6(cyclobutylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

A sample of N-cyclobutyl-N-methylamine was prepared as follows.Cyclobutylamine (5.00 g, 68.9 mmol) and potassium carbonate (13.3 g,96.5 mmol) were vigorously stirred in dry diethyl ether (250 mL) undernitrogen in an ice bath while trifluoroacetic anhydride (10.7 mL) wasadded dropwise over 20 minutes. Ice water (20 mL) was added. The etherlayer was separated, dried (MgSO₄), and concentrated to a colourlessliquid (11.50 g). This liquid was dissolved in dry acetone (170 mL) withmethyl iodide (40 g, 0.28 mole) and heated to 40° C. Powdered potassiumhydroxide (16 g, 0.28 equiv.) was added. Stirring at 40° C. wascontinued for 45 minutes. The excess methyl iodide and acetone wereremoved by evaporation and water (75 mL) was added to the residualliquid and solids. The resulting solution was brought to reflux over 15minutes (oil bath 110° C.) and maintained at reflux for 5 minutes. Thesolution was cooled to 25° C., saturated with sodium chloride, andextracted with diethyl ether (3×150 mL). The ether solution was dried(MgSO₄) and evaporated to leave colourless oil (3.72 g, 64%).

¹ H-NMR (CDCl₃) δ3.25-3.15 (m, 1, CHN), 2.34 (s, 3, NCH₃), 2.27-2.03 (m,2, 2CH), 1.8-1.6 (m, 4, CH₂ and 2CH). Such a sample ofN-cyclobutyl-N-methylamine (510 mg, 6.0 mmol) was heated with(±)-(cis)-4-(2-amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanolfrom Example 4 (544 mg, 2.00 mmol) in methanol (16 mL) in a Parr bomb at65° C. for 5.5 hours. Sodium hydroxide (1N, 2 mL) was added and thesolution evaporated to dryness. The residue was chromatographed onsilica gel. Title compound was eluted with 10% methanol-chloroform as apale yellow solid foam, from acetonitrile; 528 mg, 84%.

¹ H-NMR: (DMSO-d₆) δ7.62 (s, 1, purine H-8), 6.15-6.07 (m, 1, ═CH),6.0-5.7 (m, 4, ═CH, NH₂, and cyclobutyl CHN), 5.5-5.3 (m, 1, CHN), 4.77(t, J=5.3, 1, OH), 3.42 (m, 2, CH₂ OH), 3.27 (s, overlapped by H₂ O,N--CH₃), 2.85 (m, 1, H-1'), 2.7-2.5 (m, 1, 0.5 cyclopentyl CH₂), 2.4-2.0(m 4, 2 cyclobutyl CH₂), 1.7-1.4 (m, 3, 0.5 cyclopentyl CH₂ andcyclobutyl CH₂).

Anal. Calcd. for C₁₆ H₂₂ N₆ O..03H₂ O.0.05CH₃ CH: C, 60.08; H, 7.12; N,26.33. Found: C, 60.02, 59.97; H, 7.10, 7.13; N, 26.30, 26.26.

EXAMPLE 14(±)-cis-[4-[2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-yl)-methyl-L-valinatetrifluoroacetate

N-Butyloxycarbonyl-L-valine (1.09 g, 5.0 mmol) andN,N-dicyclohexylcarbodiimide (0.515 g, 2.5 mmol) were stirred in drymethylene-chloride (15 mL) for 1 hour. The mixture was filtered, theprecipitate was washed with methylene chloride (10 mL), and thefiltrate-wash was evaporated to dryness. To this was added(±)-cis-4-(2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolfrom Example 7 (0.600 g, 2 mmol), dry N,N-dimethylformamide (15 mL) and4-N,N-dimethylaminopyridine (5 mg, 0.04 mmol). The reaction was stirredat room temperature under nitrogen for 16 hours. H₂ O (1 mL) was addedand the solution was concentrated under vacuum. The residual oil waspartitioned between 0.1N NaOH (2 mL) and chloroform (3×50 mL). Thecombined chloroform extracts were dried (MgSO₄), solvent evaporated andthe residue chromatographed on silica gel. Elution with 5%methanol-chloroform gave the N-butyloxycarbonyl-blocked derivative ofthe title compound as a white solid (0.750 g, 75%).

¹ H-NMR: (DMSO-d₆) δ7.62 (s, 1, H-8), 7.15 (d, J=8.2, 1, NH), 6.10 and5.90 (2m, 2, CH═CH), 5.79 (br s, 2, NH₂), 5.40 (br m, 1, CH--N), 4.10(d, J=6.4, 2, CH₂ --O), 3.80 (m, 1 valyl CH--N), 3.30-3.15 (m,overlapping s at 3.23, total 4, CH--N--Me), 3.10-3.0 (br m, 1, CH),2.75-2.55 (m, 1, 0.5CH₂), 2.05-1.85 (m, 1, CHMe₂), 1.70-1.50 (m, 1,0.5CH₂), 1.34 (m, 9, CMe₃), 0.90-0.60 (m, 10, CHMe₂ and cyclopropylCH₂). Such a sample (0.74 g, 1.5 mmol) was dissolved in trifluoroaceticacid:methylene chloride/1:3 (25 mL) and the solution stirred at 25° C.under nitrogen for 30 minutes. Evaporation left the title compound as ayellow foam (0.957 g, 87%),

¹ H-NMR: (DMSO-d₆) δ8.38 (br s, 3, NH₃ +), 8.0 (s, 1, H-8), 7.80-7.10(br m, 2, NH₂), 6.18 and 6.0 (2m, 2, CH═CH), 5.48 (m, 1, CH--N), 4.26(br d, J=6.5, overlapped by H₂ O, CH₂ --O), 3.93 (br m, 1, CH--N valyl),3.55 (br s, 3, N--Me), 3.20-3.10 (br m, 2, CH and cyclopropyl CH--N),2.79-2.69 (m, 1, 0.5CH₂), 2.20-2.05 (m, 1, CHMe₂), 1.67-1.60 (m, 1,0.5CH₂), 1.10-0.90 (m, 10, 2CH₃ and 2 cyclopropyl CH₂).

Anal. Calcd. for C₂₀ H₂₉ N₇ O₂.1.0H₂ O.0.4EtOH.2.60CF₃ CO₂ H: C, 42.64;H, 4.95; N, 13.39. Found: C, 42.63; H, 4.91; N, 13.42.

EXAMPLE 15(±)-cis-4-[2-Amino-6-(cyclooctylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

(±)-cis-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol(0.549 g, 2 mmol), cyclooctylamine (0.762 g, 6 mmol) and ethanol (15 mL)were stirred at reflux under nitrogen for 20 hours. 1N NaOH (2 mL) wasadded and solvent was evaporated. The residual oil was chromatographedon silica gel. Title compound was eluted with 5% methanol-chloroform aswhite powder after crystallization from acetonitrile-methanol (0.623 g,87%); m.p. 171°-173° C.

¹ H-NMR: (DMSO-d₆) δ7.60 (s, 1H, H-8), 6.90 (m, 1, NH), 6.10 and 5.85(2m, 2, CH═CH), 5.75 (br s, 2, NH₂), 5.40 (m, 1, CHN), 4.76 (t, J=5.1,1, OH), 4.30 (br m, 1, CH--N), 3.45 (m, 2, CH₂ --O), 2.85 (br m, 1, CH),2.70-2.55 (m, 1, 1/2CH₂), 1.85-1.40 (br m, 14, 7CH₂ and 1/2CH₂).

Anal. Calcd. C₁₉ H₂₈ N₆ O: C, 64.02; H, 7.92; N, 23.58. Found: C, 64.11;H, 7.97; N, 23.51.

EXAMPLE 16(±)-cis-4-[2-Amino-6-(cyclopropylamino)-8-methyl-9H-purin-9-yl]-2-cyclopentene-1-methanol

(±)-cis-4-[(2,5-Diamino-4-chloro-6-pyrimidinyl)amino]-2-cyclopentene-1-methanolprepared as in Example 3 (1.12 g, 4.38 mmol) was stirred inN,N-dimethylformamide (5 mL) with trimethylorthoacetate (30 mL) andethane sulfonic acid (0.66 g, 5.7 mmol) at 70° C. for 3 days. Theresulting solution was evaporated to a yellow syrup. Acetic anhydride(20 mL) was added and this solution was refluxed for 2.5 hours. Theresulting dark solution was evaporated to a syrup, which was dissolvedin 1N hydrochloric acid (50 mL). After 24 hours, the pH was adjusted to6 with sodium hydroxide and most of the water evaporated. Crude productwas extracted into 20% isopropyl alcohol-chloroform. This solution wasdried (MgSO₄) and solvent evaporated to leave(±)-cis-4-(2-amino-6-chloro-8-methyl-9H-purin-9-yl)-2-cyclopentene-1-methanolas a pale yellow glass (0.30 g); structure confirmed by ¹ H-NMR. Thissample was dissolved in methanol (10 mL) and stirred in a Parr bomb withcyclopropylamine (1 mL) at 70° C. for 12 hours. Evaporation andchromatography on silica gel gave title compound, eluted as acream-colored solid foam (136 mg) with 5% methanol-chloroform.

¹ H-NMR: (DMSO-d₆) δ7.13 (d, J=4.6, 1, NH), 6.02 and 5.84 (both m, 2,CH═CH), 5.68-5.56 (m, 3, NH₂ and CH--N), 4.85 (t, 1, CH₂ OH), 3.53 (m,2, CH₂ OH), 3.02 (m, 1, CH--N of cyclopropyl), 2.88 (m, 1, CH), 2.5 (m,overlapping solvent, 0.5 cyclopentyl CH₂), 1.72 (m, 1, 0.5 cyclopentylCH₂), 0.7-0.5 (m, 4, 2 cyclopropyl CH₂).

Anal. Calcd. for C₁₅ H₂₀ N₆ O.0.25CH₃ OH.0.65H₂ O: C, 57.23; H, 7.02; N,26.26. Found: C, 57.55; H, 6.99; N, 25.95.

EXAMPLE 17(-)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 5 (0.600 g, 2.00 mmol) was dissolved in1,3-dimethyl-3,4,5,6-tetrahydro-2-(1H)-pyrimidinone (Aldrich, 12 mL).Phosphoryl chloride (0.76 mL, 8.0 mmol) was added to the stirred, cooled(-10° C.) solution. After 3 minutes, cold water (100 mL) was added andthe resulting solution neutralized with 3M ammonium hydroxide. Theneutralized solution was diluted to 1 liter with water and applied to a2.5×20 cm column of DEAE Sephadex A25 (Pharmacia) which had beenpreequilibrated with 50 mM ammonium bicarbonate. The column was firstwashed with 4 liters of 50 mM ammonium bicarbonate. The 5'-monophosphateof(±)-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolwas then eluted with a 2-liter gradient of 50 to 300 mM ammoniumbicarbonate. The fractions containing nucleotide were evaporated to awhite powder to remove ammonium bicarbonate; 71% calculated by UVabsorbance; one peak by HPLC (see below). Snake venom 5'-nucleotidase(EC 3.1.3.5) from Crotalus atrox (1000 UI, Sigma) was added to 1.4mmoles of nucleotide dissolved in water (20 mL). The solution wasincubated at 37° C. for 22 hours, at which time additional enzyme (1000IU) was added. Incubation was continued for another 3 days. HPLCanalysis (0.4×10 cm Whatman Partisil 10 strong anion exchange column;elution with a gradient of 20 mM to 1M ammonium phosphate, pH 5.5,containing 5% methanol; UV detection at 284 nM) at this point showedthat 50% of the starting nucleotide had been dephosphorylated to thenucleoside. This mixture was again applied to a DEAE Sephadex column asdescribed above. Elution with 4 liters of 50 mM ammonium bicarbonategave fractions containing the title compound. Evaporation of the waterleft white powder. This material was further purified by chromatographyon silica gel with MeOH:CHCl₃ /1:9 to give colorless glass. The glasswas solidified in acetonitrile to give(-)-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolas white gummy solid which was dried to a solid foam at 0.5 mm Hg at 68°C. (260 mg, 86% from racemate); ¹ H-NMR in DMSO-d₆ and mass spectrumidentical with those of the racemate (title compound of Example 5);[α]²⁰ _(D) -59.7°, [α]²⁰ ₄₃₆ -127.8°, [α]²⁰ ₃₆₅ -218.1°, (c=0.15,methanol).

Anal. Calcd. for C₁₄ H₁₈ N₆ O.0.8H₂ O: C, 55.91; H, 6.57; N, 27.94.Found: C, 56.05; H, 6.65; N, 27.88.

Continued elution of such a Sephadex column with a 2-liter gradient of50 to 300 mM ammonium bicarbonate gave the 5'-monophosphate (see Example19) which was stable to 5'-nucleotidase.

EXAMPLE 18 5'-Monophosphate of(-)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 17 (0.35 g, 1.2 mmol) was dissolved in1,3-dimethyl-3,4,5,6-tetrahydro-2-(1H)-pyrimidinone (Aldrich, 5 mL).Phosphoryl chloride (Aldrich, 0.43 mL, 4.6 mmol) was added to thestirred, cooled (-10° C.) solution. After 3 minutes, cold water (20 mL)was added and the resulting solution neutralized with 3M ammoniumhydroxide. Ion exchange chromatography as in Example 17 gave thenucleotide as the diammonium salt after evaporation of water, whitepowder (95% yield, quantitated by UV); HPLC analysis as in Example 17shows one peak; UV λ_(max) nM (0.1M HCl): 254, 297; (pH 7 phosphatebuffer): 259, 284; (0.1M NaOH): 259, 284. The base/phosphate ratio was1.0/1.3 as determined by the method of B. Ames (Methods in Enzymology8:115, 1966). [α]²⁰ _(D) -69.9°, [α]²⁰ ₅₇₈ -73.0°, [α]²⁰ ₅₄₆ -84.0°(c=0.52, MeOH:H₂ O/4:1).

EXAMPLE 19 5'-Monophosphate of(+)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

Elution of the DEAE Sephadex column described in Example 17 after5'-nucleotidase incubation with a 2-liter gradient of 50 to 300 mMammonium bicarbonate gave nucleotide-containing fractions which, afterevaporation of water, gave title compound as the diammonium salt; whitepowder (56% from title compound of Example 5); HPLC analysis as inExample 17 shows one peak; UV λ_(max) nM (0.1M HCl): 254, 297; (pH 7phosphate buffer): 259, 284; (0.1M NaOH): 259, 284. The base/phosphateratio was 1.0/0.98. [α]²⁰ _(D) +62.0°, [α]²⁰ ₅₇₈ +65.2°, [α]²⁰ ₅₄₆+75.0°, (c=0.54, MeOH:H₂ O/4:1).

EXAMPLE 20(+)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 19 (0.67 mmole) was dissolved in water (20mL) and alkaline phosphatase (EC 3.1.3.1) from calf intestine (3000 IU,Boehringer Mannheim) was added. The solution was incubated at 37° C. for19 hours, at which point HPLC analysis as in Example 17 showed that allof the nucleotide had been dephosphorylated. The solution was evaporatedto dryness and the residual solids extracted with refluxing ethanol (100mL). The ethanol-soluble material was adsorbed on silica gel and appliedto a silica gel column. Title compound was eluted withmethanol:chloroform/1:9. Evaporation of an acetonitrile-ethanol solutiongave white solid foam (164 mg, 79%); ¹ H-NMR in DMSO-d₆ and massspectrum identical with those of the racemate (title compound of Example5); [α]²⁰ _(D) +58.7°, [α]²⁰ ₄₃₆ +126.2°, [α]²⁰ ₃₆₅ +217.5°, (c=0.10,methanol).

Anal. Calcd. for C₁₄ H₁₈ N₆ O.0.60H₂ O.0.15EtOH: C, 56.49; H, 6.66; N,27.64. Found: C, 56.60; H, 6.63; N, 27.55.

EXAMPLE 21(-)-cis-4-[2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 7, (2.00 g, 6.50 mmol) was dissolved in1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (Aldrich, 20 mL).Phosphoryl chloride (2.28 mL, 24.0 mmol) was added to the stirred,cooled (-10° C.) solution. After 3 minutes, cold water (80 mL) wasadded. The solution was extracted with chloroform (3×80 mL). The aqueouslayer was diluted with ethanol (400 mL) and the pH adjusted to 6 withsaturated aqueous NaOH. The precipitated inorganic salts were filteredoff. The filtrate was further diluted with ethanol to a volume of 1liter and the pH adjusted to 8 with additional NaOH. The resultingprecipitate was filtered and dried to give the 5'-monophosphate of(±)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolas white powder (4.0 mmoles, 62% quantitated by UV absorbance); HPLCanalysis as in Example 17 shows one peak. This racemic 5' -monophosphatewas dissolved in water (200 mL) and snake venom 5'-nucleotidase (EC3.1.3.5) from Crotalus atrox (5,000 IU, Sigma) was added. Afterincubation at 37° C. for 10 days, HPLC analysis as in Example 17 showedthat 50% of the starting nucleotide had been dephosphorylated to thenucleoside. These were separated on a 5×14 cm column of DEAE SephadexA25 (Pharmacia) which had been preequilibrated with 50 mM ammoniumbicarbonate. Title compound was eluted with 2 liters of 50 mM ammoniumbicarbonate. Evaporation of water gave white powder which was dissolvedin methanol, adsorbed on silica gel, and applied to a silica gel column.Title compound was eluted with methanol:chloroform/1:9 as a colorlessglass. An acetonitrile solution was evaporated to give white solid foam,dried at 0.3 mm Hg over P₂ O₅ ; 649 mg (72% from racemate); ¹ H-NMR inDMSO-d₆ and mass spectrum identical with those of the racemate (titlecompound of Example 7); [α]²⁰ _(D) -48.0°, [α]²⁰ ₄₃₆ -97.1°, [α]²⁰ ₃₆₅-149° (c=0.14, methanol).

Anal. Calcd. for C₁₅ H₂₀ N₆ O.0.10CH₃ CN: C, 59.96; H, 6.72; N, 28.06.Found: C, 59.93; H, 6.76; N, 28.03.

Continued elution of the Sephadex column with 2 liters of 100 mMammonium bicarbonate and then with 2 liters of 200 mM ammoniumbicarbonate gave 5'-monophosphate (see Example 22) which was stable to5'-nucleotidase.

EXAMPLE 22(+)-cis-4-[2-Amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The fractions containing nucleotide eluted from the Sephadex column ofExample 21 were combined and alkaline phosphatase (EC 3.1.3.1) from calfintestine (4800 IU, Boehringer Mannheim) was added. The solution wasincubated at 25° C. for 18 hours, at which point HPLC analysis showedthat all of the nucleotide has been dephosphorylated. The solution wasevaporated to dryness and the residual solids extracted with refluxingethanol (100 mL). The ethanol-soluble material was adsorbed on silicagel and applied to a silica gel column. Title compound was eluted withmethanol:chloroform/1:9 as a colorless glass. An acetonitrile solutionwas evaporated to give white solid foam, dried at 0.3 mm Hg over P₂ O₅ ;659 mg (73% from racemate); ¹ H-NMR in DMSO-d₆ and mass spectrumidentical with those of the racemate (title compound of Example 7);[α]²⁰ _(D) +47.0°, [α]²⁰ ₄₃₆ +93.0°, [α]²⁰ ₃₆₅ +141.3° (c=0.11,methanol).

Anal. Calcd. for C₁₅ H₂₀ N₆ O.0.1CH₃ CN: C, 59.95; H, 6.72; N, 28.06.Found: C, 59.92; H, 6.80; N, 27.96.

EXAMPLE 23 (1S,4R)-4-Amino-2-cyclopentene-1-methanoldibenzoyl-D-tartrate

(±)-cis-4-Acetamidocyclopent-2-enemethyl acetate was hydrolyzed withbarium hydroxide as in Example 1. The resulting syrup (acetic acid saltof (±)-4-amino-2-cyclopentene-1-methanol) was converted to free amine bystirring with an excess of Amberlite IRA-400 (OH⁻) resin in water. Theresin was filtered off, washed with water, and the filtrate-washevaporated to a pale yellow syrup which was dried by evaporation ofportions of ethanol. Such a sample of amine (2.26 g, 20.0 mmol) anddibenzoyl-D-tartaric acid (Aldrich, 3.62 g, 10.0 mmol as 99%) weredissolved in hot absolute ethanol (35 mL). Refluxing acetonitrile (ca.150 mL) was added to the cloud point and the solution was allowed tocool slowly to room temperature. The white needles which formed wererecrystallized three times from the same solvent combination to givetitle compound as white plates (1.07 g, 37%); m.p. 160°-162°; [α]²⁰ _(D)+66.9°, [α]²⁰ ₄₃₆ +165°, [α]²⁰ ₃₆₅ +325° (c=0.28, methanol). X-raycrystallography of this salt allowed the absolute configuration of thecation to be fixed by the known configuration of the D-dibenzoyltartaric acid dianion. This salt crystallized in the space group C2 withone C₆ H₁₂ NO cation and one-half C₁₈ H₁₄ O₈ dianion as the asymmetricunit.

Anal. Calcd. for C₆ H₁₁ NO.1/2 (C₁₈ H₁₄ O₈): C, 61.63; H, 6.21; N, 4.79.Found: C, 61.56; H, 6.24; N, 4.74.

EXAMPLE 24 (1R,4S)-4-Amino-2-cyclopentene-1-methanoldibenzoyl-L-tartrate

This salt was formed and crystallized exactly as in Example 23, exceptthat dibenzoyl-L-tartaric acid was used. Three crystallizations fromethanol-acetonitrile gave title compound as white plates (1.00 g, 34%);m.p. 160°-162°; [α]²⁰ _(D) -68.2°, [α]²⁰ ₄₃₆ -169°, [α]²⁰ ₃₆₅ -333°,(c=0.24, methanol).

Anal. Calcd. for C₆ H₁₁ NO.1/2 (C₁₈ H₁₄ O₈): C, 61.63; H, 6.21; N, 4.79.Found: C, 61.59; H, 6.21; N, 4.76.

EXAMPLE 25(±)-cis-N-[4-chloro-5-formamido-6-[[4-(hydroxymethyl)-2-cyclopentene-1-yl]amino]-2-pyrimidinyl]acetamide

N-(5-Amino-4,6-dichloropyrimidin-2-yl)acetamide (J. Org. Chem. 1975, 40,3141) was formylated by addition of 96% formic acid (20 mL) to asolution of (0.75 g, 3.4 mmoles) dissolved in acetic anhydride (20 mL).The resulting solution was stirred at 25° C. for one hour and thenevaporated to give N-(4,6-dichloro-5-formamido-2-pyrimidinyl)acetamideas tan powder (0.77 g, 91%); structure confirmed by ¹ H-NMR and massspectrum. This tan powder (840 mg, 3.37 mmol),(±)-cis-4-amino-2-cyclopentene-1-methanol (940 mg, 8.2 mmol), andtriethylamine (0.80 g, 8.0 mmol) were warmed in ethanol (50 mL) in anoil bath (70°-80° C.) under nitrogen for 50 minutes and evaporated to adark oil which was chromatographed on silica gel. Title compound waseluted with 5% methanol-chloroform as a peach-colored solid foam (840mg). Crystallization from methanol gave white granules (575 mg, 52%);m.p. 189°-193°; ¹ H-NMR (DMSO-d₆) δ10.23 (br, 1.0, NHAc), 9.3 (br, 1.0,NHCHO), 8.15 and 7.90 (both s, total 1.0, HC═O from two conformers,peaks coalesce at 60° C.), 7.42 and 7.22 (both d, J=8.3, total 1.0,CH--NH from two conformers, peaks coalesce at 60° C.), 5.9 and 5.7 (bothm, 2.0, CH═CH), 5.05 (m, 1, CH--N), 4.73 (m, 1, OH), 3.39 (m, 2, CH₂OH), 2.72 (m, 1, CH), 2.40 (m, 1, 1/2CH₂), 1.36 (m, 1, 1/2CH₂).

Anal. Calcd. for C₁₃ H₁₆ N₅ O₃ Cl: C, 47.93; H, 4.95; N, 21.50; Cl,10.88. Found: C, 47.99; H, 4.96; N, 21.42; Cl, 10.96.

EXAMPLE 26(±)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

The title compound of Example 25 (0.91 g, 2.79 mmol) was dissolved indry DMF (1 mL). Triethylorthoformate (10 mL) and ethane sulfonic acid(0.29 mL, 3.4 mmol) were added and the solution heated at 65° C. for 24hours. The solution was evaporated to a syrup. The syrup was dissolvedin 1N HCl (15 mL) and stirred for three hours. The pH was adjusted to 7with 5N sodium hydroxide and the resulting mixture (oil formed) wasextracted with i-propanol:chloroform/1:3 (3×100 mL). The combinedorganic layers were dried (MgSO₄) and evaporated to a red glass (0.93g). A solution of this glass in methanol (20 mL) was heated withcyclopropylamine (2 mL) in a Parr bomb at 70° C. for 18 hours. Theresulting solution was evaporated to a dark glass which was adsorbed onsilica gel. Elution with 7% methanol-ethylacetate gave title compound(148 mg, 19%) as white powder, after trituration with acetonitrile; ¹H-NMR (DMSO-d₆) identical with that of the title compound of Example 5.

In the same manner, the product of Example 23 is converted to theproducts of Example 17 or Example 21 (using N-methyl-N-cyclopropylaminein the last step).

EXAMPLE 27(+)-(1R,4S)-cis-N-[4-Chloro-5-formamido-6-{[4-(hydroxymethyl)-2-cyclopentene-1-yl]amino}-2-pyrimidinyl]acetamide

(1S,4R)-4-Amino-2-cyclopentene-1-methanol dibenzoyl-D-tartrate preparedas in Example 23 (2.76 g, 9.02 mmol) was dissolved in water (20 mL) andapplied to a column of 65 mL of Amberlite IA-400 (OH⁻ form) anionexchange resin. The column was washed with water. Basic fractions werecombined and evaporated to a residual oil which was dried by evaporationof absolute ethanol and then at 0.5 mm to give(1S,4R)-4-amino-2-cyclopentene-1-methanol (1.2 g) as a pale yellow oil(darkens rapidly in air) which was used immediately. This oil wasdissolved in ethanol (5 mL) and added to a solution ofN-(4,6-dichloro-5-formamido-2-pyrimidinyl)acetamide (2.07 g, 8.31 mmol),prepared as described in Example 25, and triethylamine (2.50 g, 24.8mmol). The resulting dark solution was heated (oil bath 75°-80° C.)under nitrogen for 50 minutes. The solution was evaporated to a syrupwhich was applied to a silica gel column.

Title compound was eluted with 3 to 5% methanol-chloroform as a paleyellow solid foam (1.59 g, 54%); ¹ H-NMR identical with that ofcrystallized sample. Such a sample was crystallized from ethanol to givewhite granules, m.p. 194°-195° C.; ¹ H-NMR (DMSO-d₆) identical with thatof the title compound of Example 25; [α]²⁰ _(D) +2.7°, [α]²⁰ ₅₇₈ +3.6°,[α]²⁰ ₅₄₆ +2.9°, [α]²⁰ ₄₃₆ -2.5°, [α]²⁰ ₃₆₅ -41.2°.

EXAMPLE 28(-)-(1S,4R)-cis-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol

Title compound of Example 27 (1.15 g, 3.53 mmol) was gently refluxed indiethoxylmethyl acetate (45 mL) under nitrogen for 3.5 hours. Theresulting pale yellow solution was concentrated at 0.5 mm Hg to a yellowsyrup. The syrup was stirred in 1N HCl (50 mL) for 1.0 hour. Thissolution was neutralized with sodium bicarbonate and evaporated todryness. The residual solids were extracted with methanol and themethanol-soluble material applied to a silica gel column. Elution of thecolumn with 10% methanol-ethyl acetate gave title compound as a paleyellow solid foam (730 mg), 78%); ¹ H-NMR (DMSO-d₆): identical with thatof racemate (title compound of Example 4); [α]²⁰ _(D) -114.9° (c=0.26,MeOH).

EXAMPLE 29(-)-(1S,4R)-cis-4-[2-Amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol

Title compound of Example 28 (560 mg, 2.11 mmol) in methanol (12 mL) washeated with cyclopropylamine (2.4 mL) in a Parr bomb at 78° C. for 17hours. The solvent was evaporated and the residue chromatographed onsilica gel. Title compound was eluted with 5-7% methanol-ethyl acetateas a colorless solid foam (367 mg, 59%); ¹ H-NMR (DMSO-d₆) identicalwith that of Example 17; [α]²⁰ _(D) -59.0° (c=0.28, MeOH) confirms theabsolute configuration of the title compound of Example 17.

EXAMPLE 30 (1S,4R)-4-Amino-2-cyclopentene-1-methanoldibenzoyl-D-tartrate

2-Azabicyclo[2.2.1]hept-5-en-3-one [Daluge and Vince, J. Org. Chem.1978, 43, 2311 and U.S. Pat. No. 4,268,672] (44.0 g, 0.400 mole) wasstirred in 2N HCl in methanol (0.5 L) at 25° C. for 1.5 hours. Volatileswere evaporated to leave(±)-cis-methyl-4-amino-2-cyclopentene-1-carboxylate hydrochloride as anoff-white powder (71.1 g). Trituration of such a sample withdiethylether gave white powder, m.p. 92.5°-95° C. [J. Org. Chem. 1981,46, 3271; m.p. 82°-83° C.]; ¹ H-NMR (DMSO-d₆) δ8.25 (br s, 3, NH₃ +),6.1 and 5.9 (both m, 2, CH═CH), 3.64 (s) overlapping 3.75-3.6 (m, total4, OMe and CH), 2.65-2.45 and 2.05-1.85 (both m, 2, CH₂).

Anal. Calcd for C₇ H₁₁ NO₂.HCl: C, 47.33; H, 6.81; N, 7.89; Cl, 19.96.Found: C, 47.41; H, 6.84; N, 7.85; Cl, 19.89.

(±)-cis-Methyl-4-amino-2-cyclopentene-1-carboxylate hydrochloride (17.7g, 0.100 mole) and diisobutyl-aluminum hydride (0.500 mole as a 1Msolution in hexane) were refluxed in hexane (200 mL) for 6 hours. Theresulting solution was cooled and 10 mL of 1M aqueous ammonium chlorideand then methanol (200 mL) were added. This mixture was refluxed for 30minutes and MgSO₄ (10 g) added. Solids were filtered off and washed withadditional methanol. The filtrate-wash was evaporated to a dark oil(15.5 g); ¹ H-NMR (DMSO-d₆) identical to that of(±)-4-amino-2-cyclopentene-1-methanol prepared as described in Example23. Such a sample, after purification by chromatography on silica gel(EtOH:CHCl₃ :NH₄ OH/10:90:1) was crystallized to the salt withdibenzoyl-D-tartaric acid (title compound of Example 23).

EXAMPLE 31(-)-(1S,4R)-cis-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanolA. (±)-cis-4-(2,6-Diamino-9H-purin-9-yl)-2-cyclopentene-1-methanol

(±)-(1α,4α)-4-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol(1.50 g, 5.65 mmol) and ammonia (1, 35 ml) were stirred at 70° C. in aParr bomb for 48 hours. Evaporation left crude product which waspurified by elution from a silica gel column with 10%methanol-chloroform (1.27 g, 91%). Crystallization of such a sample fromacetonitrile-methanol gave white granules, m.p. 145°-147° C.; ¹ H-NMR(Me₂ SO-d₆) δ7.59 (s, 1, purine H-8), 6.60 (br s, 2, NH₂), 6.09 and 5.85(both m, 2, CH═CH), 5.71 (br s, 2, NH₂), 5.36 (m, 1, CH--N), 4.71 (t,J=5.4, 1, OH), 3.50-3.35 (m, 2, CH₂ --O), 2.85 (m, 1, H-1'), 2.60 and1.57 (both m, 2, CH₂).

Anal. Calcd. C₁₁ H₁₄ N₆ O: C, 53.65; H, 5.73; N, 34.13 Found: C, 53.79;H, 5.79; N, 34.00.

B. (1R,4S)-9-(4-Hydroxymethyl-2-cyclopentenyl)guanine

(±)-cis-4-(2,6-Diamino-9H-purin-9-yl)-2-cyclopentene-1-methanol (1.26 g,5.12 mmol) was dissolved in 514 mL of 0.02M potassium phosphate buffer(pH 7.4) with 16.4×10³ units of calf intestinal adenosine deaminase(adenosine aminohydrolase EC 3.5.4.4 Boehringer Mannheim). After 6.5hours at 25° C., the reaction was quenched by addition of an equalvolume of methanol. The solution was evaporated to dryness and theresidual solids extracted with hot methanol (4×100 ml). The contents ofthe methanol extracts was adsorbed on silica gel and loaded on a silicagel column packed in 10% MeOH-CHCl₃. Elution with 10% MeOH-CHCl₃ (400ml) gave unreacted starting material (0.66 g). Crystallization frommethanol-acetonitrile gave white granules of(+)-cis-4-(2,6-diamino-9H-purin-9-yl)-2-cyclopentene-1-methanol (0.38g); m.p. 175°-178° C.; ¹ H-NMR (Me₂ SO-d₆) identical with that ofstarting material; [α]²⁰ _(D) +85.1° (c=0.19 in methanol). Continuedelution of the column with 20-25% methanol chloroform (300 mL) gave, onevaporation, a white powder (0.62 g). Recrystallization from water gavetitle compound as white needles (0.56 g, 84%); m.p. >320° C.; ¹ H-NMR(Me₂ SO-d₆) δ10.54 (br s, 1, NHC═O), 7.59 (s, 1, H-8), 6.43 (br s, 2,NH₂), 6.1 and 5.8 (both m, 2, CH═CH), 5.3 (m, 1, CH--N), 4.73 (t, J=5.3,1, OH), 3.43 (t, J=5.6, 2, CH₂ --O), 2.8-2.6 (m, 1, H-4'), 2.65-2.55 and1.60-1.50 (both m, 2, CH₂); [α]²⁰ _(D) -96.3° (c=0.11 in 0.01NNaOH:MeOH/2:3); [α]²⁰ _(D) -63.9°, (c=0.16, MeOH).

Anal. Calcd. C₁₁ H₁₃ N₅ O₂.0.7H₂ O: C, 50.84; H, 5.59; N, 26.95. Found:C, 50.90; H, 5.63; N, 26.83.

C.(1S,4R)-[4-(2-Amino-1,6-dihydro-6-oxo-9H-purin-9-yl)-2-cyclopenten-1-yl]methylacetate

(1R,4S)-9-(4-Hydroxymethyl-2-cyclopentenyl)guanine (150 mg, 0.607mmole), acetic anhydride (freshly distilled, 65 mg, 0.161 mmole),4-dimethylaminopyridine (3 mg), and dry dimethylformamide (5 mL) werestirred under nitrogen for 2 days. The solvent was evaporated and theresidue applied to a silica gel column. Title compound was eluted with10% methanol-chloroform as a waxy white solid. Crystallization fromethanol gave white powder (123 mg, 70%), m.p. 247°-249° C.; ¹ H-NMR(DMSO-d₆) δ10.55 (br s, 1, NHCO), 7.55 (s, 1, purine H-8), 6.42 (br s,2, NH₂), 6.06 and 5.94 (both m, 2, CH═CH), 5.34 (m, 1, CH--N), 4.07 (d,J=6.0, 2, CH₂ O), 3.05 (m, 1, CH), 2.6 and 1.55 (both m, 2, CH₂), 1.98(s, 3, COCH₃).

Anal. Calcd. for C₁₃ H₁₅ N₅ O₃ : C, 53.97; H, 5.23; N, 24.21. Found: C,53.85; H, 5.25; N, 24.12.

D.(-)-(1S,4R)-cis-(2-Amino-6-chloro-9H-purin-9-yl)-2-cyclopentene-1-methanol

(1S,4R)-[4-(2-Amino-1,6-dihydro-6-oxo-9H-purin-9-yl)-2-cyclopenten-1-yl]methylacetate (50 mg, 0.17 mmole), phosphoryl chloride (2 mL), and N,N-diethylaniline (38 μL) were refluxed for 3 minutes. Volatiles were evaporated,and ice-water (5 mL) was added to the residual oil. The solution wasneutralized and extracted with methylene chloride (3×20 mL). Themethylene chloride layers were dried (MgSO₄) and evaporated to givecrude product. Chromatography on silica gel (5% methanol-chloroform)gave(1S,4R)-[4-(2-amino-6-chloro-9H-purin-9-yl)-2-cyclopenten-1-yl]methylacetate as pale yellow crystals from ethyl acetate, m.p. 124°-127°; ¹H-NMR (DMSO-d₆) 8.01 (s, 1, purine H-8), 6.90 (s, 2, NH₂), 6.11 and 5.99(both m, 2, CH═CH), 5.46 (m, 1, CH--N), 4.06 (d, J=6.2, 2, CH₂ O), 3.1(m, 1, CH--N), 2.7 and 1.65 (both m, 2, CH₂), 1.98 (s, 3, CH₃ CO).

Deacetylation in ammonia-methanol provides the title compound of Example28.

EXAMPLE 32[cis-4-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopenten-1-yl]methylR-2,3-bis-(hexadecanoyloxy)propyl hydrogen phosphate

A solution of L-α-dipalmitoyl phosphatidyl choline (150 mg, 0.2 mmol,Sigma) in 6 mL of chloroform was added to a flask containing(±)-cis-4-(2-amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanol(300 mg, 1.03 mmol), phospholipase D, Type VII (from Streptomyces, 1.0mg, specific activity 185 units/mg, Sigma) and pH 4.5 buffer (1.5 mL,250 mM in CaCl₂, 200 mM in NaOAc adjusted to pH 4.5 by addition of 0.1NHCl). The resulting biphase was stirred at 45° C. (oil bath) for 1 hour.The layers were separated and the aqueous layer extracted withchloroform (3×6 mL). The combined organic layers were washed with 1NHCl, dried and concentrated. Such a sample was purified by elution from2 silica gel columns with 12% methanol-chloroform to yield the titlecompound, 120 mg (47%). This material was solidified usingethylacetate-acetonitrile to produce a light yellow powder m.p.155°-157° C.; ¹ H-NMR (CD₃ CD-CDCl₃) δ7.78 (s, overlapping solvent,purine H-8), 6.12 and 5.88 (m, 2, HC═CH), 5.53 (m, 1, CHN cyclopentene),5.22 (m, 1, CO₂ CH), 4.37 (dd, J=3, 12; 1, 1/2POCH₂ glycerol), 4.12 (m,1, 1/2POCH₂ glycerol), 3.42 (m, 4, OCH₂ glycerol, OCH₂), 3.11 (br m, 1,CH), 2.90 (m, 1, NCH), 2.78 (m, 1, 1/2CH₂ cyclopentene), 2.27 (m, 4,2CH₂ CO₂), 1.70 (m, 1, 1/2CH₂ cyclopentene), 1.56 (br m, 4, 2CH₂ CH₂CO₂), 1.27 (br m, 38, 24CH₂), 0.88 (m, 6, 2CH₃), 0.83 (m, 2, CH₂cyclopropyl), 0.60 (m, 2, CH₂ cyclopropyl).

Anal. Calcd. for C₄₉ H₈₅ N₆ O₈ P.2.4H₂ O: C, 61.28; H, 9.42; N, 8.75; P,3.22. Found: C, 60.97; H, 9.12; N, 8.78; P, 2.96.

The preceding example is an adaptation of the procedure by Satoshi Shutoet al. Tetrahedron Letters, Vol. 28, No. 2, pp. 199-202, 1987.

EXAMPLE 33[cis-4-(2-Amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopenten-1-yl]methylR-2,3-bis-(hexanoyloxy)propyl hydrogen phosphate

A solution of L-α-dicaproyl phosphatidylcholine (300 mg, 0.66 mmol,Sigma) in 15 mL of CHCl₃ was added to a flask containing(±)-cis-4-(2-amino-6-(cyclopropylamino)-9H-purin-9-yl)-2-cyclopentene-1-methanol(378 mg, 1.32 mmol), phospholipase D, Type VII (from Streptomyces, 1.04mg, specific activity 185 units/mg, Sigma), pH 4.5 buffer (4.5 mL, 250mM in CaCl₂, 200 mM in NaOAc adjusted to pH 4.5 with HCl) and CHCl₃ (3mL). The resulting biphase was stirred at 45° C. (oil bath) for 4 hours.The layers were separated and the organic layer washed with 1N HCl (2×4mL). The combined aqueous layers were back washed with chloroform (10mL). The combined organic layers were dried (MgSO₄) and concentrated.The residue was placed on a silica gel column and the title compound waseluted with 16% methanol-chloroform and concentrated to yield a fineyellow powder. This material was dissolved in ethanol and concentrated(3×50 mL) before drying under high vacuum to yield 103 mg (21% yield) ofa light yellow powder, m.p. 182°-185° C.

¹ H-NMR: (DMSO-d₆) δ7.61 (s, 1, purine H-8), 7.22 (br s, 1, NH), 6.09(m, 1, 1/2CH═CH), 5.89 (m, overlapping br s at 5.83, 3, 1/2CH═CH, NH₂),5.41 (br m, 1, CHN), 5.09 (br m, 1, CO₂ CH), 4.30 (dd; J=2.7, 12; 1,1/2POCH₂ glycerol), 4.08 (m, 1, 1/2POCH₂ glycerol), 3.80 (br moverlapping br m at 3.75, 4, OCH₂ glycerol, OCH₂), 3.02 (br m, 2, CH,NCH cyclopropyl), 2.65 (m, 1, 1/2CH₂ cyclopentene), 2.23 (+, J=7.5, 4,2CH₂ CO₂), 1.48 (br m, 5, 2CH₂ CH₂ CO₂, 1/2CH₂ cyclopentene), 1.23 (brm, 8, 2 (CH₂)₂), 0.84 (m, 6, 2CH₃), 0.67 and 0.58 (m, 4, 2CH₂cyclopropyl).

Anal. Calcd. for C₂₉ H₄₅ N₆ O₈ P.3.9H₂ O, 0.2CHCl₃, 0.05EtOH: C, 48.00;H, 7.33; N, 11.46; Cl, 2.9. Found: C, 48.65; H, 6.61; N, 10.81; Cl, 2.5.

The preceding example is an adaptation of the procedure by Satoshi Shutoet al. Tetrahedron Letters, Vol. 28, No. 2, pp. 199-202, 1987.

EXAMPLE A Tablet Formulations

The following formulations A, B and C are prepared by wet granulation ofthe ingredients with a solution of povidone, followed by addition ofmagnesium stearate and compression.

    ______________________________________                                        Formulation A     mg/tablet mg/tablet                                         ______________________________________                                        (a)   Active ingredient                                                                             250       250                                           (b)   Lactose B.P.    210       26                                            (c)   Povidone B.P.   15         9                                            (d)   Sodium Starch   20        12                                                  Glycollate                                                              (e)   Magnesium Stearate                                                                             5         3                                                                  500       300                                           ______________________________________                                    

    ______________________________________                                        Formulation B     mg/tablet mg/tablet                                         ______________________________________                                        (a)   Active ingredient                                                                             250       250                                           (b)   Lactose         150       --                                            (c)   Avicel PH 101   60        26                                            (d)   Povidone B.P.   15         9                                            (e)   Sodium Starch   20        12                                                  Glycollate                                                              (f)   Magnesium Stearate                                                                             5         3                                                                  500       300                                           ______________________________________                                    

    ______________________________________                                        Formulation C    mg/tablet                                                    ______________________________________                                        Active ingredient                                                                              100                                                          Lactose          200                                                          Starch            50                                                          Povidone          5                                                           Magnesium stearate                                                                              4                                                                            359                                                          ______________________________________                                    

The following formulations, D and E, are prepared by direct compressionof the admixed ingredients. The lactose in formulation E is of thedirect compression type (Dairy Crest--"Zeparox").

    ______________________________________                                        Formulation D       mg/tablet                                                 ______________________________________                                        Active ingredient   250                                                       Pregelatinised Starch NF15                                                                        150                                                                           400                                                       ______________________________________                                    

    ______________________________________                                        Formulation E   mg/tablet                                                     ______________________________________                                        Active ingredient                                                                             250                                                           Lactose         150                                                           Avicel          100                                                                           500                                                           ______________________________________                                    

Formulation F (Controlled Release Formulation)

The formulation is prepared by wet granulation of the ingredients(below) with a solution of povidone followed by the addition ofmagnesium stearate and compression.

    ______________________________________                                                             mg/tablet                                                ______________________________________                                        (a)     Active ingredient  500                                                (b)     Hydroxypropylmethylcellulose                                                                     112                                                        (Methocel K4M Premium)                                                (c)     Lactose B.P.        53                                                (d)     Povidone B.P.       28                                                (e)     Magnesium Stearate  7                                                                            700                                                ______________________________________                                    

Drug release takes place over a period of about 6-8 hours and iscomplete after 12 hours.

EXAMPLE B Capsule Formulations Formulation A

A capsule formulation is prepared by admixing the ingredients ofFormulation D in Example A above and filling into a two-part hardgelatin capsule. Formulation B (infra) is prepared in a similar manner.

    ______________________________________                                        Formulation B         mg/capsule                                              ______________________________________                                        (a)      Active ingredient                                                                              250                                                 (b)      Lactose B.P.     143                                                 (c)      Sodium Starch Glycollate                                                                        25                                                 (d)      Magnesium Stearate                                                                              2                                                                            420                                                 ______________________________________                                    

    ______________________________________                                        Formulation C       mg/capsule                                                ______________________________________                                        (a)       Active ingredient                                                                           250                                                   (b)       Macrogol 4000 B.P.                                                                          350                                                                           600                                                   ______________________________________                                    

Capsules of formulation C are prepared by melting the Macrogol 4000 BP,dispersing the active ingredient in the melt and filling the melt into atwo-part hard gelatin capsule.

    ______________________________________                                        Formulation D    mg/capsule                                                   ______________________________________                                        Active ingredient                                                                              250                                                          Lecithin         100                                                          Arachis Oil      100                                                                           450                                                          ______________________________________                                    

Capsules of formulation D are prepared by dispersing the activeingredient in the lecithin and arachis oil and filling the dispersioninto soft, elastic gelatin capsules.

Formulation E (Controlled Release Capsule)

The following controlled release capsule formulation is prepared byextruding ingredients a, b and c using an extruder, followed byspheronisation of the extrudate and drying. The dried pellets are thencoated with release-controlling membrane (d) and filled into atwo-piece, hard gelatin capsule.

    ______________________________________                                                            mg/capsule                                                ______________________________________                                        (a)      Active ingredient                                                                              250                                                 (b)      Microcrystalline Cellulose                                                                     125                                                 (c)      Lactose B.P.     125                                                 (d)      Ethyl Cellulose   13                                                                           513                                                 ______________________________________                                    

EXAMPLE C Injectable Formulation

    ______________________________________                                        Formulation A.                                                                ______________________________________                                        Active ingredient         0.200   g                                           Hydrochloric acid solution, 0.1 M, or                                         Sodium hydroxide solution, 0.1 M q.s. to pH                                                             4.0 to 7.0                                          Sterile water q.s. to     10      ml                                          ______________________________________                                    

The active ingredient is dissolved in most of the water (35°-40° C.) andthe pH adjusted to between 4.0 and 7.0 with the hydrochloric acid or thesodium hydroxide as appropriate. The batch is then made up to volumewith the water and filtered through a sterile micropore filter into asterile 10 ml amber glass vial (type 1) and sealed with sterile closuresand overseals.

    ______________________________________                                        Formulation B.                                                                ______________________________________                                        Active ingredient         0.125  g                                            Sterile, pyrogen-free, pH 7 phosphate                                         buffer q.s. to            25     ml                                           ______________________________________                                    

EXAMPLE D

    ______________________________________                                        Intramuscular injection                                                       ______________________________________                                        Active ingredient       0.20 g                                                Benzyl Alcohol          0.10 g                                                Glycofurol 75           1.45 g                                                Water for Injection q.s. to                                                                           3.00 ml                                               ______________________________________                                    

The active ingredient is dissolved in the glycofurol. The benzyl alcoholis then added and dissolved, and water added to 3 ml. The mixture isthen filtered through a sterile micropore filter and sealed in sterile 3ml amber glass vials (type 1).

EXAMPLE E

    ______________________________________                                        Syrup                                                                         ______________________________________                                        Active ingredient      0.25    g                                              Sorbitol Solution      1.50    g                                              Glycerol               2.00    g                                              Sodium Benzoate        0.005   g                                              Flavor, Peach 17.42.3169                                                                             0.0125  ml                                             Purified Water q.s. to 5.00    ml                                             ______________________________________                                    

The active ingredient is dissolved in a mixture of the glycerol and mostof the purified water. An aqueous solution of the sodium benzoate isthen added to the solution, followed by addition of the sorbitolsolution and finally the flavor. The volume is made up with purifiedwater and mixed well.

EXAMPLE F

    ______________________________________                                        Suppository              mg/suppository                                       ______________________________________                                        Active ingredient (631 m)*                                                                              250                                                 Hard Fat, BP (Witepsol H15 - Dynamit NoBel)                                                            1770                                                                          2020                                                 ______________________________________                                         *The active ingredient is used as a powder wherein at least 90% of the        particles are of 631 m diameter or less.                                 

One-fifth of the Witepsol H15 is melted in a steam-jacketed pan at 45°C. maximum. The active ingredient is sifted through a 200 μm sieve andadded to the molten base with mixing, using a silverson fitted with acutting head, until a smooth dispersion is achieved. Maintaining themixture at 45° C., the remaining Witepsol, H15 is added to thesuspension and stirred to ensure a homogenous mix. The entire suspensionis passed through a 250 μm stainless steel screen and, with continuousstirring, is allowed to cool to 40° C. At a temperature of 38° C. to 40°C., 2.02 g of the mixture is filled into suitable, 2 ml plastic molds.The suppositories are allowed to cool to room temperature.

EXAMPLE G

    ______________________________________                                        Pessaries          mg/pessary                                                 ______________________________________                                        Active ingredient (631 m)                                                                        250                                                        Anhydrate Dextrose 380                                                        Potato Starch      363                                                        Magnesium Stearate  7                                                                            1000                                                       ______________________________________                                    

The above ingredients are mixed directly and pessaries prepared bydirect compression of the resulting mixture.

Antiviral Activity

The compound of Example 5 was tested for anti-HIV activity in MT₄ cellsaccording to the method described by Averett, D. R., J. Virol. Methods,23 1989, 263-276 and was found to have an IC₅₀ value of 21±12 μM (13determinations). The IC₅₀ value of the compound of Example 17 was 3.6 μM(an average of two determinations).

I claim:
 1. A compound of formula (I): ##STR4## wherein R³ representshydrogen or C₁₋₆ alkyl; R⁶ represents C₃₋₈ cycloalkyl, and R⁷ representsa hydrogen atom or a branched or straight chain C₁₋₆ alkyl; or apharmaceutically acceptable ester or a pharmaceutically acceptable saltthereof.
 2. A compound, ester or salt of formula (I) according to claim1 in which R³ is hydrogen, R⁶ is C₃₋₆ cycloalkyl and R⁷ is methyl orhydrogen.
 3. A compound according to claim 2 in which R⁶ is cyclopropyl.4. A compound of formula (I) according to claim 1 selectedfrom:(-)-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanoland(-)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolor racemic or partially resolved mixtures with the (+)-cis enantiomersthereof.5. 5.(±)-cis-4-[2-amino-6-(cyclopropylamino-9H-purin-9-yl]-2-cyclopentene-1-methanol.6.(-)-cis-4-[2-amino-6-(cyclopropylamino-9H-purin-9-yl]-2-cyclopentene-1-methanol.7. A pharmaceutically acceptable salt of a compound according to claims5 or
 6. 8. A pharmaceutically acceptable ester of a compound accordingto claims 5 or
 6. 9. A compound of formula (I) according to claim 1wherein the pharmaceutically acceptable ester is a mono-, di-, ortri-phosphate ester or a pharmaceutically acceptable salt thereof.
 10. Acompound of formula (I) according to claim 1 wherein thepharmaceutically acceptable ester is the L-valinate or a salt thereof.11. A compound, ester or salt of claim 3, in which the pharmaceuticallyacceptable ester is a mono-, di, or tri-phosphate ester or apharmaceutically acceptable salt thereof.
 12. A compound of the formula(I): R1 ? ? ##STR5## wherein R⁷ is hydrogen, R⁶ is cyclopropyl and R³ ishydrogen or a pharmaceutically acceptable salt thereof.
 13. A compoundof the formula (I): ##STR6## wherein R⁷ is methyl, R⁶ is cyclopropyl andR³ is hydrogen or a pharmaceutically acceptable salt thereof.
 14. Atablet or capsule containing the compound of claim
 12. 15. A tablet orcapsule containing the compound of claim
 13. 16.(±)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol.17.(-)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol.18. A pharmaceutical formulation comprising a compound of formula (I) asdefined in claim 1 or a pharmaceutically acceptable ester or apharmaceutically acceptable salt thereof and a pharmaceuticallyacceptable carrier therefor.
 19. A formulation according to claim 18wherein the compound of formula (I) is selectedfrom:(-)-cis-4-[2-amino-6-(cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanoland(-)-cis-4-[2-amino-6-(cyclopropylmethylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanolor racemic or partially resolved mixtures with the (+)-cis enantiomersthereof.
 20. A tablet or capsule containing 50 to 700 mg of a compoundaccording to claims 5 or 6 or a pharmaceutically acceptable salt or apharmaceutically acceptable ester thereof.